CA2878584C - Cable comprising twisted sinusoid for use in distributed sensing - Google Patents
Cable comprising twisted sinusoid for use in distributed sensing Download PDFInfo
- Publication number
- CA2878584C CA2878584C CA2878584A CA2878584A CA2878584C CA 2878584 C CA2878584 C CA 2878584C CA 2878584 A CA2878584 A CA 2878584A CA 2878584 A CA2878584 A CA 2878584A CA 2878584 C CA2878584 C CA 2878584C
- Authority
- CA
- Canada
- Prior art keywords
- cable
- fiber optic
- wavelength
- fiber
- sinusoid
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
- 239000000835 fiber Substances 0.000 claims abstract description 59
- 238000000034 method Methods 0.000 claims abstract description 9
- 239000013307 optical fiber Substances 0.000 claims abstract description 9
- 238000012545 processing Methods 0.000 abstract description 2
- 238000005259 measurement Methods 0.000 description 6
- 238000012544 monitoring process Methods 0.000 description 6
- 101150118300 cos gene Proteins 0.000 description 5
- 101100234408 Danio rerio kif7 gene Proteins 0.000 description 4
- 101100221620 Drosophila melanogaster cos gene Proteins 0.000 description 4
- 101100398237 Xenopus tropicalis kif11 gene Proteins 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 230000003287 optical effect Effects 0.000 description 3
- 230000035945 sensitivity Effects 0.000 description 3
- 238000013459 approach Methods 0.000 description 2
- 239000012530 fluid Substances 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 230000001902 propagating effect Effects 0.000 description 2
- 101100007330 Saccharomyces cerevisiae (strain ATCC 204508 / S288c) COS2 gene Proteins 0.000 description 1
- 229920000535 Tan II Polymers 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000005489 elastic deformation Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000004807 localization Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000003208 petroleum Substances 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
- G01H9/00—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means
- G01H9/004—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means using fibre optic sensors
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
- G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
- G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
- G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
- G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
- G01D5/35338—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using other arrangements than interferometer arrangements
- G01D5/35354—Sensor working in reflection
- G01D5/35358—Sensor working in reflection using backscattering to detect the measured quantity
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
- G01V1/00—Seismology; Seismic or acoustic prospecting or detecting
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/44—Mechanical structures for providing tensile strength and external protection for fibres, e.g. optical transmission cables
- G02B6/4401—Optical cables
- G02B6/441—Optical cables built up from sub-bundles
- G02B6/4413—Helical structure
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Geophysics And Detection Of Objects (AREA)
- Length Measuring Devices By Optical Means (AREA)
- Length Measuring Devices With Unspecified Measuring Means (AREA)
- Optical Transform (AREA)
Abstract
A distributed fiber optic cable comprises an elongate body and a first optical fiber longitudinally housed in the body, wherein the fiber describes a sinusoid having an amplitude and a first wavelength along the length of the body and wherein the sinusoid rotates along the length of the body so as to describe a twisted sinusoid having a twist wavelength. A method for sensing an acoustic wave comprises a) providing a set of signals collected from the cable, b) processing the signals so as to divide the fiber in each twist wavelength of cable into a predetermined number of channels, c) measuring the amplitudes in each channel and calculating the maximum and minimum amplitude in a preselected length of cable, d) using the calculated maximum and minimum for the preselected length of cable to determine the amplitude and direction of the wave at the preselected length of cable.
Description
=
CABLE COMPRISING TWISTED SINUSOID FOR USE IN
DISTRIBUTED SENSING
RELATED CASES
This case is related to U.S. Application Serial No. 61/576,192, filed 15 December 2011 and entitled "Detecting Broadside Acoustic Signals With A Fiber Optical Distributed Acoustic Sensing (Das) Assembly".
FIELD OF THE INVENTION
[0001] The invention relates to fiber optic devices and in particular to a fiber optical Distributed Acoustic Sensing (DAS) assembly that is adapted to sense the magnitude and direction of acoustic signals, and particularly those signals that are travelling at an angle or substantially perpendicular to the device.
BACKGROUND OF THE INVENTION
CABLE COMPRISING TWISTED SINUSOID FOR USE IN
DISTRIBUTED SENSING
RELATED CASES
This case is related to U.S. Application Serial No. 61/576,192, filed 15 December 2011 and entitled "Detecting Broadside Acoustic Signals With A Fiber Optical Distributed Acoustic Sensing (Das) Assembly".
FIELD OF THE INVENTION
[0001] The invention relates to fiber optic devices and in particular to a fiber optical Distributed Acoustic Sensing (DAS) assembly that is adapted to sense the magnitude and direction of acoustic signals, and particularly those signals that are travelling at an angle or substantially perpendicular to the device.
BACKGROUND OF THE INVENTION
[0002] Various attempts have been made to provide sensing capabilities in the context of petroleum exploration, production, and monitoring, with varying degrees of success.
Recently, these attempts have included the use of fiber optic cables to detect acoustic energy.
Because the cables typically comprise optically conducting fiber containing a plurality of backscattering inhomogeneities along the length of the fiber, such systems allow the distributed measurement of optical path length changes along an optical fiber by measuring backscattered light from a laser pulse input into the fiber. Because they allow distributed sensing, such systems may be referred to as "distributed acoustic sensing" or "DAS" systems. One use of DAS systems is in seismic applications, in which seismic sources at known locations transmit acoustic signals into the formation, and/or passive seismic sources emit acoustic energy. The signals are received at seismic sensors after passing through and/or reflecting through the formation. The received signals can be processed to give information about the formation through which they passed. This technology can be used to record a variety of seismic information. Another application is in the field of in-well applications and acoustic fluid monitoring.
Recently, these attempts have included the use of fiber optic cables to detect acoustic energy.
Because the cables typically comprise optically conducting fiber containing a plurality of backscattering inhomogeneities along the length of the fiber, such systems allow the distributed measurement of optical path length changes along an optical fiber by measuring backscattered light from a laser pulse input into the fiber. Because they allow distributed sensing, such systems may be referred to as "distributed acoustic sensing" or "DAS" systems. One use of DAS systems is in seismic applications, in which seismic sources at known locations transmit acoustic signals into the formation, and/or passive seismic sources emit acoustic energy. The signals are received at seismic sensors after passing through and/or reflecting through the formation. The received signals can be processed to give information about the formation through which they passed. This technology can be used to record a variety of seismic information. Another application is in the field of in-well applications and acoustic fluid monitoring.
[0003] DAS systems typically detect backscattering of short (1 - 10 meter) laser pulses from impurities or inhomogeneities in the optical fiber. If fiber is deformed by an incident seismic wave then 1) the distance between impurities changes and 2) the speed of the laser pulses changes. Both of these effects influence the backscattering process. By observing changes in the backscattered signal it is possible to reconstruct the seismic wave amplitude.
The first of the above effects appears only if the fiber is stretched or compressed axially.
The second effect is present in case of axial as well as radial fiber deformations. The second effect is, however, several times weaker than the first. Moreover, radial deformations of the fiber are significantly damped by materials surrounding the fiber. As a result, a conventional DAS
system with a straight fiber is mainly sensitive to seismic waves polarized along the cable axis, such as compression (P) waves propagating along the cable or shear (S) waves propagating perpendicular to the cable. The strength of the signal varies approximately as cos- 0, where is the angle between the fiber axis and the direction of wave propagation (for P
waves). Thus, while there exists a variety of commercially available DAS systems that have varying sensitivity, dynamic range, spatial resolution, linearity, etc., all of these systems are primarily sensitive to axial strain. Acoustic signals travelling normal to the fiber axis may sometimes be referred to as "broadside" signals and, for P waves, result in radial strain on the fiber.
Thus, as the angle between direction of travel of the acoustic signal and the fiber axis approaches 90 , DAS
cables become much less sensitive to the signal and may even fail to detect it. The Appendix attached hereto provides further discussion of the mathematics of sinusoidal fibers.
The first of the above effects appears only if the fiber is stretched or compressed axially.
The second effect is present in case of axial as well as radial fiber deformations. The second effect is, however, several times weaker than the first. Moreover, radial deformations of the fiber are significantly damped by materials surrounding the fiber. As a result, a conventional DAS
system with a straight fiber is mainly sensitive to seismic waves polarized along the cable axis, such as compression (P) waves propagating along the cable or shear (S) waves propagating perpendicular to the cable. The strength of the signal varies approximately as cos- 0, where is the angle between the fiber axis and the direction of wave propagation (for P
waves). Thus, while there exists a variety of commercially available DAS systems that have varying sensitivity, dynamic range, spatial resolution, linearity, etc., all of these systems are primarily sensitive to axial strain. Acoustic signals travelling normal to the fiber axis may sometimes be referred to as "broadside" signals and, for P waves, result in radial strain on the fiber.
Thus, as the angle between direction of travel of the acoustic signal and the fiber axis approaches 90 , DAS
cables become much less sensitive to the signal and may even fail to detect it. The Appendix attached hereto provides further discussion of the mathematics of sinusoidal fibers.
[0004] Hence, it is desirable to provide an improved cable that is more sensitive to signals travelling normal to its axis and enables distinguishing radial strain from the axial strain.
Sensitivity to broadside waves is particularly important for seismic or microseismic applications, with cables on the surface or downhole. In addition to broadside sensitivity, it is also desirable to provide three-component (3C) sensing, from which the direction of travel of the sensed signal can be determined.
SUMMARY OF THE INVENTION
Sensitivity to broadside waves is particularly important for seismic or microseismic applications, with cables on the surface or downhole. In addition to broadside sensitivity, it is also desirable to provide three-component (3C) sensing, from which the direction of travel of the sensed signal can be determined.
SUMMARY OF THE INVENTION
[0005] In accordance with preferred embodiments of the invention there is provided a distributed fiber optic cable comprising an elongate body and a first optical fiber longitudinally housed in the body, wherein the fiber describes a sinusoid having an amplitude and a first wavelength along the length of the body and wherein the sinusoid rotates along the length of the body so as to describe a twisted sinusoid having a twist wavelength.
100061 The cable may provides a plurality of sensing channels and the first wavelength may be a function of a desired channel length. The first wavelength may also be a function of the amplitude.
[0007] The first wavelength may be between 0.001 and 0.1 m, between 0.005 and 0.1 m, or more preferably between 0.005 and 0.05 m. The twist wavelength may be between 1 m and 50 m, between 2 m and 20 m, or more preferably approximately 10 m.
[0008] The fiber optic cable may define a helix.
[0009] The amplitude may be a function of the thickness of the body.
100101 The invention further provides a method for sensing an acoustic wave, comprising a) providing a set of signals collected from a distributed fiber optic cable comprising an elongate body and a first optical fiber longitudinally housed in said body, wherein the fiber describes a sinusoid having an amplitude and a first wavelength along the length of the body and wherein the sinusoid rotates along the length of the body so as to describe a twisted sinusoid having a twist wavelength, b) processing the signals so as to divide the fiber in each twist wavelength of cable into a predetermined number of channels, c) measuring the amplitudes in each channel and calculating the maximum and minimum amplitude in a preselected length of cable, and d) using the calculated maximum and minimum for the preselected length of cable to determine the amplitude and direction of the wave at the preselected length of cable.
100111 The preselected length of cable in step c) may be equal to one-half of the twist wavelength. The twist wavelength may be between 1 m and 50 m and the predetermined number of channels may be 10. The twist wavelength is between 2 m and 20 m.
More preferably, the twist wavelength is 10 m and the preselected length of cable in step c) is 5 m.
10011a] According to one aspect of the present invention, there is provided a fiber optic cable for a fiber optic distributed acoustic sensing assembly, comprising: an elongate body;
and a first optical fiber longitudinally housed in said body, wherein the fiber defmes a sinusoid having an amplitude and a first wavelength, wherein the sinusoid passes through a length axis of said body, and wherein the sinusoid rotates about the length axis of the body and wherein the sinusoid rotates along the length of the body so as to define a twisted sinusoid having a twist wavelength.
[0011b] According to another aspect of the present invention, there is provided a method for optically sensing an acoustic wave using a fiber optic distributed acoustic sensing assembly, comprising the steps of providing the fiber optic cable of claim 1, and measuring backscattered light from a laser pulse input into the first optical fiber in the fiber optic cable.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] For a more detailed understanding of the invention, reference is made to the accompanying Figures wherein:
Figure 1 is a schematic view of a triangular prism having a sinusoidal path along each of its longitudinal surfaces;
Figure 2 is a schematic view of a coordinate system;
Figure 3 is an illustration of a possible combination of coordinate systems;
3a õ õ.. .
100061 The cable may provides a plurality of sensing channels and the first wavelength may be a function of a desired channel length. The first wavelength may also be a function of the amplitude.
[0007] The first wavelength may be between 0.001 and 0.1 m, between 0.005 and 0.1 m, or more preferably between 0.005 and 0.05 m. The twist wavelength may be between 1 m and 50 m, between 2 m and 20 m, or more preferably approximately 10 m.
[0008] The fiber optic cable may define a helix.
[0009] The amplitude may be a function of the thickness of the body.
100101 The invention further provides a method for sensing an acoustic wave, comprising a) providing a set of signals collected from a distributed fiber optic cable comprising an elongate body and a first optical fiber longitudinally housed in said body, wherein the fiber describes a sinusoid having an amplitude and a first wavelength along the length of the body and wherein the sinusoid rotates along the length of the body so as to describe a twisted sinusoid having a twist wavelength, b) processing the signals so as to divide the fiber in each twist wavelength of cable into a predetermined number of channels, c) measuring the amplitudes in each channel and calculating the maximum and minimum amplitude in a preselected length of cable, and d) using the calculated maximum and minimum for the preselected length of cable to determine the amplitude and direction of the wave at the preselected length of cable.
100111 The preselected length of cable in step c) may be equal to one-half of the twist wavelength. The twist wavelength may be between 1 m and 50 m and the predetermined number of channels may be 10. The twist wavelength is between 2 m and 20 m.
More preferably, the twist wavelength is 10 m and the preselected length of cable in step c) is 5 m.
10011a] According to one aspect of the present invention, there is provided a fiber optic cable for a fiber optic distributed acoustic sensing assembly, comprising: an elongate body;
and a first optical fiber longitudinally housed in said body, wherein the fiber defmes a sinusoid having an amplitude and a first wavelength, wherein the sinusoid passes through a length axis of said body, and wherein the sinusoid rotates about the length axis of the body and wherein the sinusoid rotates along the length of the body so as to define a twisted sinusoid having a twist wavelength.
[0011b] According to another aspect of the present invention, there is provided a method for optically sensing an acoustic wave using a fiber optic distributed acoustic sensing assembly, comprising the steps of providing the fiber optic cable of claim 1, and measuring backscattered light from a laser pulse input into the first optical fiber in the fiber optic cable.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] For a more detailed understanding of the invention, reference is made to the accompanying Figures wherein:
Figure 1 is a schematic view of a triangular prism having a sinusoidal path along each of its longitudinal surfaces;
Figure 2 is a schematic view of a coordinate system;
Figure 3 is an illustration of a possible combination of coordinate systems;
3a õ õ.. .
6 PCT/US2013/052647 Figure 4 is a diagram showing orientation of the r)-axis with respect to the prism coordinate system; and Figure 5 is a schematic illustration of a twisted strip in accordance with an embodiment of the invention.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
[0013] An initial analysis starts with a configuration in which three sinusoidal fibers lie in the three longitudinal surfaces of a triangular prism as shown below. All three fibers are assumed to have the same shape.
[0014] A coordinate system (x, y, z) is chosen such that the z axis is directed along the prism, and x- and y-axes lie in its cross-section. One of the prism sides lies in the (x, z) plane, as illustrated in Figure 2 . Two other sides lie in the (x', z) and (x÷, z) planes. The x' and x"
axes are rotated with respect the x-axis on angles ii = 60 and iv - 71 = 1200 correspondingly.
[0015] Generally speaking, the strain tensor eik has 6 independent components.
Using three fibers one can do only 3 independent measurements. These 3 measurements are not sufficient to deduce 6 unknown components of the strain tensor.
[0016] One way to obtain sufficient data may be to combine triangular bodies to form a larger body, as shown in Figure 3. If the angles are selected to provide sufficient information, all 6 unknown components of the strain tensor may be calculated.
[0017] However, the strain tensor can be determined uniquely if with particular types of elastic deformations are assumed. In most geophysical application one measures primary seismic waves. The waves coming from distant targets can be approximately considered as plane waves.
Transformation of the Strain Sensor [0018] Suppose that a plane primary wave propagates along the c,-axis.
Orientation of the L.:-axis with respect to the prism coordinate system can be specified by two angles, 0 and cp, as is shown in Figure 4. The strain tensor has only one component ec.L., in the coordinate system where (; and r are arbitrary axes so that the three axes c;-,11 and c form and orthogonal basis. Components of the strain tensor in two different coordinate systems are related as &xi&11 , a:K? axfi (3>.!
elex' .e" -77i-Te" 7.7 7-Tr, -737 - ;
/t's ON + th? LiX"'flv d'effe"
e,.
&t; , " \ 4)-4 "
From which it follows that = sirt2 cos2 e,?5, .Ã=!Fy = ec-c: sin2 sin2 (2) = ee;z: si n2 0 sill 0 COS e = ecos20.
[0019] in what follows that e is positive and it refers to the maximum strain in the wave.
Equation (2) shows that the strain tensor in plane primary waves is fully determined by three variables: etx, 0, and cp, that can be reconstructed from three independent measurements.
Transition between the coordinate systems (x', y', z) and (x, y, z) is given by the equations = x cos 0 y sin 0, = sift 0 --I- y cos 0. (3) Using Eq. (3) and Eq. (1), gives evx; = cos2 0 ex, + 2 sin .0 cos -0 exy sin2 en,. (4) The expression for ex, ,x,, is obtained by making the replacement yr- r is Eq. (4), ex)exn = COS4v =e.õ2g ¨ 2 sif-up cos 0 exy Sirl2 (5) Twisted Sinusoid [0020] Another approach is to use a single twisted strip, so that its orientation angle i, varies with z. The signal measured by this strip is equal to (18) S(P) = (COS2 exx 2 sin lb COS exy sin2 Taking the derivative of S with respect to angle itç gives d5 ¨ eyy) + 2 cos 20 (19) Using Eq. (2) to calculate components of the strain tensor, reduces Eq. (19) to dS
¨dz = CCW sirt p(0 - (20) The signal has extrema at the points where dS/dz = 0, i.e. at = Oanci = 0 (7T/ 2) It is straightforward to check that the signal has a maximum at = (band a minimum at 0 (7c/ 2). The correspondent values of the signal are equal to Sma, = etc ((a: sin2 0 + cos2 cos2 O.
(23) From Eq. 23 it follows that SpNay ---- Strip tan2 = = . (24) Solving Eq. 24 and substituting th.e result into Eq. 23 allows one to reconstruct ea.
Example [0021] A hypothetical cable has a radius for outer fibers with a 30-degree wrapping angle of 17.4 mm. A flat strip with a sinusoidal fiber described in the plane of the strip by:
v(r) = a.stri(bx). = a.. in (co) with x = the inline distance along the strip. For a strip length of x = 27t/b, the length of the fiber equals 1). , 4 _______ t ________________________________________________ (oh) ____________________________________ . E
[0022] E is a complete elliptic integral of the second kind, which can be expressed as a power series.
[0023] Continuing the hypothetical, a channel is required every 2 m along the cable, while the channel length measured along the fiber is 8 m. Using a = 0.0174 m, it can be calculated that 343.5 sinusoids need to be fitted into 2 m, corresponding to a wavelength Xi =
0.0183 m.
[0024] A flat strip is only sensitive in the x- and y-directions, but by twisting the strip it can be made sensitive to all 3 directions. Figure 5 (not to scale) illustrates a twisted strip.
[0025] Assuming that the strip is twisted by it radians over a distance X2 =
10 m, within each m there will be 10m/2m = 5 measurements, each with a different rotation along the cable axis, and each stepping on average by 180/5 = 36 degrees.
[0026] It may further be assumed that over the distance k2 the incident seismic wave is 5 approximately a plane wave. For the highest frequencies in the groundroll this assumption may not be optimal, but otherwise it is reasonable.
[0027] As set out in detail above, by measuring the amplitudes over these 5 channels per 10 m and determining (e.g. by interpolation) the maximum and minimum amplitudes, it is possible to determine all 3 components of a wavefield using a single fiber. Reliability of the 10 .. amplitudes measurements is essential in this process.
[0028] There is a risk that the fiber may bend instead of being compressed in the desired geometry, i.e. with an amplitude in the strip of 1.74 cm and a sinusoid length of 1.83 cm.
Since at least 5 sample points per 10 m are required, (the maximum station spacing assuming plane waves), a maximum of 2 m are available for the channel spacing along the cable. If it were possible to shift the channels between time samples by a fraction of a m, it would be possible to use large channel spacings along the cable, resulting in longer sinusoid lengths and reduced risk of bending of the fiber.
[0029] In preferred embodiments, the cable described herein is used on the earth's surface for detecting/monitoring seismic signals travelling through the subsurface. Thus, it may be used in conjunction with a ground anchor such as is known in the art. Similarly, the cable may be used in one or more boreholes to for detecting/monitoring detect seismic signals travelling through the subsurface.
[0030] In addition to the various applications mentioned above, the cables described herein can be used as towed streamer cables or deployed on the seabed (OBC).
[0031] The embodiments described herein can be used advantageously alone or in combination with each other and/or with other fiber optic concepts. The methods and apparatus described herein can be used to measure arrival times and waveforms of acoustic signals and in particular broadside acoustic waves. Arrival times and waveforms give information about the formation and can be used in various seismic techniques.
.. [0032] In still other applications, the methods and apparatus described herein can be used to detect microseisms and the data collected using the present invention, including broadside wave signals, can be used in microseismic localization. In these embodiments, the data are
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
[0013] An initial analysis starts with a configuration in which three sinusoidal fibers lie in the three longitudinal surfaces of a triangular prism as shown below. All three fibers are assumed to have the same shape.
[0014] A coordinate system (x, y, z) is chosen such that the z axis is directed along the prism, and x- and y-axes lie in its cross-section. One of the prism sides lies in the (x, z) plane, as illustrated in Figure 2 . Two other sides lie in the (x', z) and (x÷, z) planes. The x' and x"
axes are rotated with respect the x-axis on angles ii = 60 and iv - 71 = 1200 correspondingly.
[0015] Generally speaking, the strain tensor eik has 6 independent components.
Using three fibers one can do only 3 independent measurements. These 3 measurements are not sufficient to deduce 6 unknown components of the strain tensor.
[0016] One way to obtain sufficient data may be to combine triangular bodies to form a larger body, as shown in Figure 3. If the angles are selected to provide sufficient information, all 6 unknown components of the strain tensor may be calculated.
[0017] However, the strain tensor can be determined uniquely if with particular types of elastic deformations are assumed. In most geophysical application one measures primary seismic waves. The waves coming from distant targets can be approximately considered as plane waves.
Transformation of the Strain Sensor [0018] Suppose that a plane primary wave propagates along the c,-axis.
Orientation of the L.:-axis with respect to the prism coordinate system can be specified by two angles, 0 and cp, as is shown in Figure 4. The strain tensor has only one component ec.L., in the coordinate system where (; and r are arbitrary axes so that the three axes c;-,11 and c form and orthogonal basis. Components of the strain tensor in two different coordinate systems are related as &xi&11 , a:K? axfi (3>.!
elex' .e" -77i-Te" 7.7 7-Tr, -737 - ;
/t's ON + th? LiX"'flv d'effe"
e,.
&t; , " \ 4)-4 "
From which it follows that = sirt2 cos2 e,?5, .Ã=!Fy = ec-c: sin2 sin2 (2) = ee;z: si n2 0 sill 0 COS e = ecos20.
[0019] in what follows that e is positive and it refers to the maximum strain in the wave.
Equation (2) shows that the strain tensor in plane primary waves is fully determined by three variables: etx, 0, and cp, that can be reconstructed from three independent measurements.
Transition between the coordinate systems (x', y', z) and (x, y, z) is given by the equations = x cos 0 y sin 0, = sift 0 --I- y cos 0. (3) Using Eq. (3) and Eq. (1), gives evx; = cos2 0 ex, + 2 sin .0 cos -0 exy sin2 en,. (4) The expression for ex, ,x,, is obtained by making the replacement yr- r is Eq. (4), ex)exn = COS4v =e.õ2g ¨ 2 sif-up cos 0 exy Sirl2 (5) Twisted Sinusoid [0020] Another approach is to use a single twisted strip, so that its orientation angle i, varies with z. The signal measured by this strip is equal to (18) S(P) = (COS2 exx 2 sin lb COS exy sin2 Taking the derivative of S with respect to angle itç gives d5 ¨ eyy) + 2 cos 20 (19) Using Eq. (2) to calculate components of the strain tensor, reduces Eq. (19) to dS
¨dz = CCW sirt p(0 - (20) The signal has extrema at the points where dS/dz = 0, i.e. at = Oanci = 0 (7T/ 2) It is straightforward to check that the signal has a maximum at = (band a minimum at 0 (7c/ 2). The correspondent values of the signal are equal to Sma, = etc ((a: sin2 0 + cos2 cos2 O.
(23) From Eq. 23 it follows that SpNay ---- Strip tan2 = = . (24) Solving Eq. 24 and substituting th.e result into Eq. 23 allows one to reconstruct ea.
Example [0021] A hypothetical cable has a radius for outer fibers with a 30-degree wrapping angle of 17.4 mm. A flat strip with a sinusoidal fiber described in the plane of the strip by:
v(r) = a.stri(bx). = a.. in (co) with x = the inline distance along the strip. For a strip length of x = 27t/b, the length of the fiber equals 1). , 4 _______ t ________________________________________________ (oh) ____________________________________ . E
[0022] E is a complete elliptic integral of the second kind, which can be expressed as a power series.
[0023] Continuing the hypothetical, a channel is required every 2 m along the cable, while the channel length measured along the fiber is 8 m. Using a = 0.0174 m, it can be calculated that 343.5 sinusoids need to be fitted into 2 m, corresponding to a wavelength Xi =
0.0183 m.
[0024] A flat strip is only sensitive in the x- and y-directions, but by twisting the strip it can be made sensitive to all 3 directions. Figure 5 (not to scale) illustrates a twisted strip.
[0025] Assuming that the strip is twisted by it radians over a distance X2 =
10 m, within each m there will be 10m/2m = 5 measurements, each with a different rotation along the cable axis, and each stepping on average by 180/5 = 36 degrees.
[0026] It may further be assumed that over the distance k2 the incident seismic wave is 5 approximately a plane wave. For the highest frequencies in the groundroll this assumption may not be optimal, but otherwise it is reasonable.
[0027] As set out in detail above, by measuring the amplitudes over these 5 channels per 10 m and determining (e.g. by interpolation) the maximum and minimum amplitudes, it is possible to determine all 3 components of a wavefield using a single fiber. Reliability of the 10 .. amplitudes measurements is essential in this process.
[0028] There is a risk that the fiber may bend instead of being compressed in the desired geometry, i.e. with an amplitude in the strip of 1.74 cm and a sinusoid length of 1.83 cm.
Since at least 5 sample points per 10 m are required, (the maximum station spacing assuming plane waves), a maximum of 2 m are available for the channel spacing along the cable. If it were possible to shift the channels between time samples by a fraction of a m, it would be possible to use large channel spacings along the cable, resulting in longer sinusoid lengths and reduced risk of bending of the fiber.
[0029] In preferred embodiments, the cable described herein is used on the earth's surface for detecting/monitoring seismic signals travelling through the subsurface. Thus, it may be used in conjunction with a ground anchor such as is known in the art. Similarly, the cable may be used in one or more boreholes to for detecting/monitoring detect seismic signals travelling through the subsurface.
[0030] In addition to the various applications mentioned above, the cables described herein can be used as towed streamer cables or deployed on the seabed (OBC).
[0031] The embodiments described herein can be used advantageously alone or in combination with each other and/or with other fiber optic concepts. The methods and apparatus described herein can be used to measure arrival times and waveforms of acoustic signals and in particular broadside acoustic waves. Arrival times and waveforms give information about the formation and can be used in various seismic techniques.
.. [0032] In still other applications, the methods and apparatus described herein can be used to detect microseisms and the data collected using the present invention, including broadside wave signals, can be used in microseismic localization. In these embodiments, the data are
7 used to generate coordinates of a microseism. In still other applications, ability of the present systems to detect broadside waves and axial waves distinguishably can be used in various DAS applications, including but not limited to intruder detection, monitoring of traffic, pipelines, or other environments, and monitoring of various conditions in a borehole, including fluid inflow.
[0033] While preferred embodiments have been disclosed and described, it will be understood that various modifications can be made thereto without departing from the scope of the invention as set out in the claims that follow.
[0033] While preferred embodiments have been disclosed and described, it will be understood that various modifications can be made thereto without departing from the scope of the invention as set out in the claims that follow.
8
Claims (11)
1. A fiber optic cable for a fiber optic distributed acoustic sensing assembly, comprising:
an elongate body; and a first optical fiber longitudinally housed in said body, wherein the fiber defines a sinusoid having an amplitude and a first wavelength, wherein the sinusoid passes through a length axis of said body, and wherein the sinusoid rotates about the length axis of the body and wherein the sinusoid rotates along the length of the body so as to define a twisted sinusoid having a twist wavelength.
an elongate body; and a first optical fiber longitudinally housed in said body, wherein the fiber defines a sinusoid having an amplitude and a first wavelength, wherein the sinusoid passes through a length axis of said body, and wherein the sinusoid rotates about the length axis of the body and wherein the sinusoid rotates along the length of the body so as to define a twisted sinusoid having a twist wavelength.
2. The fiber optic cable of claim 1 wherein the cable provides a plurality of sensing channels and wherein the first wavelength is a function of a desired channel length.
3. The fiber optic cable of claim 2 wherein the first wavelength is further a function of the amplitude.
4. The fiber optic cable of claim 2 wherein the first wavelength is between 0.001 and 0.1 m.
5. The fiber optic cable of claim 2 wherein the first wavelength is between 0.005 and 0.1 m.
6. The fiber optic cable of claim 2 wherein the first wavelength is between 0.005 and 0.05 m.
7. The fiber optic cable of claim 1 wherein the cable defines a helix.
8. The fiber optic cable of claim 1 wherein the amplitude is a function of the thickness of the body.
9. The fiber optic cable of claim 1 wherein the twist wavelength is between 1 m and 50 m.
10. The fiber optic cable of claim 1 wherein the twist wavelength is between 2 m and 20 m.
11. A method for optically sensing an acoustic wave using a fiber optic distributed acoustic sensing assembly, comprising the steps of providing the fiber optic cable of claim 1, and measuring backscattered light from a laser pulse input into the first optical fiber in the fiber optic cable.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US201261678482P | 2012-08-01 | 2012-08-01 | |
| US61/678,482 | 2012-08-01 | ||
| PCT/US2013/052647 WO2014022346A1 (en) | 2012-08-01 | 2013-07-30 | Cable comprising twisted sinusoid for use in distributed sensing |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2878584A1 CA2878584A1 (en) | 2014-02-06 |
| CA2878584C true CA2878584C (en) | 2020-09-08 |
Family
ID=50028465
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA2878584A Active CA2878584C (en) | 2012-08-01 | 2013-07-30 | Cable comprising twisted sinusoid for use in distributed sensing |
Country Status (4)
| Country | Link |
|---|---|
| US (2) | US10088353B2 (en) |
| CA (1) | CA2878584C (en) |
| GB (1) | GB2519009B (en) |
| WO (1) | WO2014022346A1 (en) |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2014201313A1 (en) | 2013-06-13 | 2014-12-18 | Schlumberger Canada Limited | Fiber optic distributed vibration sensing with directional sensitivity |
| AU2015283817B2 (en) * | 2014-06-30 | 2019-11-21 | Commonwealth Scientific And Industrial Research Organisation | Deformation measurement method and apparatus |
| CA2971438A1 (en) | 2014-12-23 | 2016-06-30 | Shell Internationale Research Maatschappij B.V. | Method of and system for creating a seismic profile |
| MX2019005978A (en) | 2016-12-22 | 2019-08-12 | Halliburton Energy Services Inc | Creating 3c distributed acoustic sensing data. |
| BR112020025667A2 (en) | 2018-06-20 | 2021-03-23 | Pgs Geophysical As | long-distance acquisition |
| US12072461B2 (en) | 2019-10-28 | 2024-08-27 | Pgs Geophysical As | Modified simultaneous long-offset acquisition with improved low frequency performance for full wavefield inversion |
| GB2592703B (en) * | 2019-10-28 | 2022-11-02 | Pgs Geophysical As | Long-offset acquisition with improved low frequency performance for full wavefield inversion |
| US12105240B2 (en) | 2019-10-28 | 2024-10-01 | Pgs Geophysical As | Long-offset acquisition with improved low frequency performance for full wavefield inversion |
Family Cites Families (72)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2352315A1 (en) | 1976-05-21 | 1977-12-16 | Cables De Lyon Geoffroy Delore | OPTICAL FIBER CABLE AND IMPLEMENTATION METHOD |
| US4568408A (en) * | 1980-03-20 | 1986-02-04 | Optelecom, Inc. | Fiber optic energy sensor and optical demodulation system and methods of making same |
| US4524436A (en) | 1981-05-15 | 1985-06-18 | Schlumberger Technology Corporation | Pressure wave fiber optic transducer cable |
| US4634852A (en) * | 1982-04-14 | 1987-01-06 | The Board Of Trustees Of The Leland Stanford Junior University | Sensor using fiber optic interferometer |
| CA2134771A1 (en) | 1993-03-11 | 1994-09-15 | Philip Sutton | Method for manufacturing optical components with periodic or quasi-periodic optical properties |
| AU665490B2 (en) | 1993-05-28 | 1996-01-04 | Litton Industries Inc. | Fiber optic planar hydrophone |
| EP1355170A3 (en) | 1997-05-02 | 2004-06-09 | Sensor Highway Limited | A method of controlling production from a wellbore |
| US6281489B1 (en) | 1997-05-02 | 2001-08-28 | Baker Hughes Incorporated | Monitoring of downhole parameters and tools utilizing fiber optics |
| US20040043501A1 (en) | 1997-05-02 | 2004-03-04 | Baker Hughes Incorporated | Monitoring of downhole parameters and chemical injection utilizing fiber optics |
| US6787758B2 (en) | 2001-02-06 | 2004-09-07 | Baker Hughes Incorporated | Wellbores utilizing fiber optic-based sensors and operating devices |
| US6211964B1 (en) | 1997-10-09 | 2001-04-03 | Geosensor Corporation | Method and structure for incorporating fiber optic acoustic sensors in a seismic array |
| US6004639A (en) | 1997-10-10 | 1999-12-21 | Fiberspar Spoolable Products, Inc. | Composite spoolable tube with sensor |
| US6923273B2 (en) | 1997-10-27 | 2005-08-02 | Halliburton Energy Services, Inc. | Well system |
| NO308681B1 (en) | 1998-06-19 | 2000-10-09 | Cit Alcatel | Seismic cable with integrated sensor housing and the electrical and optical conductors arranged externally around the sensor housing |
| US6853780B1 (en) * | 1999-03-31 | 2005-02-08 | Pirelli Cavi E Sistemi S.P.A. | Optical cable for telecommunications |
| US6269198B1 (en) * | 1999-10-29 | 2001-07-31 | Litton Systems, Inc. | Acoustic sensing system for downhole seismic applications utilizing an array of fiber optic sensors |
| US6601671B1 (en) | 2000-07-10 | 2003-08-05 | Weatherford/Lamb, Inc. | Method and apparatus for seismically surveying an earth formation in relation to a borehole |
| WO2004034096A2 (en) | 2002-10-04 | 2004-04-22 | Sabeus Photonics, Inc. | Rugged fiber optic array |
| GB2396211B (en) | 2002-10-06 | 2006-02-22 | Weatherford Lamb | Multiple component sensor mechanism |
| WO2004081509A1 (en) | 2003-03-05 | 2004-09-23 | Shell Internationale Research Maatschappij B.V. | Coiled optical fiber assembly for measuring pressure and/or other physical data |
| GB2400906B (en) | 2003-04-24 | 2006-09-20 | Sensor Highway Ltd | Distributed optical fibre measurements |
| US6840114B2 (en) | 2003-05-19 | 2005-01-11 | Weatherford/Lamb, Inc. | Housing on the exterior of a well casing for optical fiber sensors |
| US6874361B1 (en) | 2004-01-08 | 2005-04-05 | Halliburton Energy Services, Inc. | Distributed flow properties wellbore measurement system |
| US7245791B2 (en) | 2005-04-15 | 2007-07-17 | Shell Oil Company | Compaction monitoring system |
| GB0605066D0 (en) | 2006-03-14 | 2006-04-26 | Schlumberger Holdings | Method and apparatus for monitoring structures |
| EP1854959B1 (en) * | 2006-05-12 | 2008-07-30 | Services Pétroliers Schlumberger | Method and apparatus for locating a plug within the well |
| US7740064B2 (en) | 2006-05-24 | 2010-06-22 | Baker Hughes Incorporated | System, method, and apparatus for downhole submersible pump having fiber optic communications |
| US7954560B2 (en) | 2006-09-15 | 2011-06-07 | Baker Hughes Incorporated | Fiber optic sensors in MWD Applications |
| MX2010001555A (en) | 2007-08-10 | 2010-03-11 | Schlumberger Technology Bv | Methods and systems of installing cable for measurement of a physical parameter. |
| US8380021B2 (en) | 2007-09-06 | 2013-02-19 | Shell Oil Company | High spatial resolution distributed temperature sensing system |
| US7946341B2 (en) | 2007-11-02 | 2011-05-24 | Schlumberger Technology Corporation | Systems and methods for distributed interferometric acoustic monitoring |
| US8520195B2 (en) | 2007-11-26 | 2013-08-27 | Schlumberger Technology Corporation | Method and system for estimating fluid leak flow rates using distributed optical fiber sensors |
| GB2456300B (en) | 2008-01-08 | 2010-05-26 | Schlumberger Holdings | Monitoring system for pipelines or risers in floating production installations |
| GB2457278B (en) | 2008-02-08 | 2010-07-21 | Schlumberger Holdings | Detection of deposits in flow lines or pipe lines |
| US7668411B2 (en) | 2008-06-06 | 2010-02-23 | Schlumberger Technology Corporation | Distributed vibration sensing system using multimode fiber |
| GB0811705D0 (en) | 2008-06-26 | 2008-07-30 | Schlumberger Holdings | Method and system for estimating fluid leak flow rates using distributed optical fibre sensors |
| GB2462096A (en) | 2008-07-23 | 2010-01-27 | Schlumberger Holdings | Monitoring of a pipeline pig using external acoustic sensors |
| GB0815297D0 (en) | 2008-08-21 | 2008-09-24 | Qinetiq Ltd | Conduit monitoring |
| US20120179390A1 (en) | 2008-09-24 | 2012-07-12 | Stephen Kimmiau | Distributed fibre optic diagnosis of riser integrity |
| WO2010053931A1 (en) | 2008-11-06 | 2010-05-14 | Schlumberger Canada Limited | Distributed acoustic wave detection |
| GB0820658D0 (en) | 2008-11-12 | 2008-12-17 | Rogers Alan J | Directionality for distributed event location (del) |
| US8245780B2 (en) | 2009-02-09 | 2012-08-21 | Shell Oil Company | Method of detecting fluid in-flows downhole |
| US20100207019A1 (en) | 2009-02-17 | 2010-08-19 | Schlumberger Technology Corporation | Optical monitoring of fluid flow |
| GB0905986D0 (en) | 2009-04-07 | 2009-05-20 | Qinetiq Ltd | Remote sensing |
| CN104295290B (en) | 2009-05-27 | 2017-04-12 | 光学感应器控股有限公司 | Fracture monitoring |
| GB2516782B (en) | 2009-05-27 | 2015-06-17 | Silixa Ltd | Method of flow monitoring |
| US8131121B2 (en) | 2009-07-07 | 2012-03-06 | At&T Intellectual Property I, L.P. | Optical fiber pipeline monitoring system and method |
| GB0912851D0 (en) | 2009-07-23 | 2009-08-26 | Fotech Solutions Ltd | Distributed optical fibre sensing |
| GB2476449B (en) | 2009-09-18 | 2013-12-11 | Optasense Holdings Ltd | Wide area seismic detection |
| GB0917150D0 (en) | 2009-09-30 | 2009-11-11 | Qinetiq Ltd | Phase based sensing |
| US20110088462A1 (en) | 2009-10-21 | 2011-04-21 | Halliburton Energy Services, Inc. | Downhole monitoring with distributed acoustic/vibration, strain and/or density sensing |
| GB0919902D0 (en) | 2009-11-13 | 2009-12-30 | Qinetiq Ltd | Improvements in fibre optic cables for distributed sensing |
| GB0919906D0 (en) | 2009-11-13 | 2009-12-30 | Qinetiq Ltd | Improvements to distributed fibre optic sensing |
| GB0919904D0 (en) | 2009-11-13 | 2009-12-30 | Qinetiq Ltd | Determining lateral offset in distributed fibre optic acoustic sensing |
| GB0919899D0 (en) | 2009-11-13 | 2009-12-30 | Qinetiq Ltd | Fibre optic distributed sensing |
| GB0921062D0 (en) | 2009-12-02 | 2010-01-13 | Qinetiq Ltd | Phased based sensing |
| WO2011079107A2 (en) | 2009-12-23 | 2011-06-30 | Shell Oil Company | Detecting broadside and directional acoustic signals with a fiber optical distributed acoustic sensing (das) assembly |
| AU2010334866B2 (en) | 2009-12-23 | 2014-09-04 | Shell Internationale Research Maatschappij B.V. | Method and system for enhancing the spatial resolution of a fiber optical distributed acoustic sensing assembly |
| US9846103B2 (en) | 2010-05-12 | 2017-12-19 | Schlumberger Technology Corporation | Oilfield conduit leakage detection system |
| EP2386881B1 (en) | 2010-05-12 | 2014-05-21 | Weatherford/Lamb, Inc. | Sonic/acoustic monitoring using optical distributed acoustic sensing |
| US8605542B2 (en) | 2010-05-26 | 2013-12-10 | Schlumberger Technology Corporation | Detection of seismic signals using fiber optic distributed sensors |
| GB201008823D0 (en) | 2010-05-26 | 2010-07-14 | Fotech Solutions Ltd | Fluid flow monitor |
| US8505625B2 (en) | 2010-06-16 | 2013-08-13 | Halliburton Energy Services, Inc. | Controlling well operations based on monitored parameters of cement health |
| NO2418466T3 (en) | 2010-06-17 | 2018-06-23 | ||
| US9476760B2 (en) | 2010-06-25 | 2016-10-25 | Schlumberger Technology Corporation | Precision measurements in a fiber optic distributed sensor system |
| US20120020184A1 (en) | 2010-07-26 | 2012-01-26 | Colin Wilson | Using a distributed optical acoustic sensor to position an object |
| CN102136994B (en) | 2010-08-02 | 2014-04-30 | 华为技术有限公司 | Label switched path creation method, system and node equipment |
| US8924158B2 (en) | 2010-08-09 | 2014-12-30 | Schlumberger Technology Corporation | Seismic acquisition system including a distributed sensor having an optical fiber |
| GB201020359D0 (en) | 2010-12-01 | 2011-01-12 | Qinetiq Ltd | Selsmic surveying |
| US9052230B2 (en) | 2011-05-13 | 2015-06-09 | Chevron U.S.A. Inc | Industrial process monitoring and imaging |
| BR112013033299A2 (en) | 2011-06-24 | 2019-09-24 | Prad Research And Development Limited | cable to monitor a tubular structure, and cable to monitor an underwater pipe |
| CN107976709B (en) | 2011-12-15 | 2019-07-16 | 国际壳牌研究有限公司 | (DAS) combine detection transverse direction acoustical signal is sensed with optical fiber distributed acoustic |
-
2013
- 2013-07-30 WO PCT/US2013/052647 patent/WO2014022346A1/en active Application Filing
- 2013-07-30 GB GB1500112.6A patent/GB2519009B/en active Active
- 2013-07-30 CA CA2878584A patent/CA2878584C/en active Active
- 2013-07-30 US US14/418,393 patent/US10088353B2/en active Active
-
2018
- 2018-06-21 US US16/014,670 patent/US10788359B2/en active Active
Also Published As
| Publication number | Publication date |
|---|---|
| US20180299322A1 (en) | 2018-10-18 |
| GB2519009A (en) | 2015-04-08 |
| US10088353B2 (en) | 2018-10-02 |
| WO2014022346A1 (en) | 2014-02-06 |
| US20150260567A1 (en) | 2015-09-17 |
| US10788359B2 (en) | 2020-09-29 |
| AU2013296677A8 (en) | 2015-03-19 |
| GB2519009B (en) | 2017-09-13 |
| CA2878584A1 (en) | 2014-02-06 |
| AU2013296677A1 (en) | 2015-03-12 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CA2878584C (en) | Cable comprising twisted sinusoid for use in distributed sensing | |
| US10139269B2 (en) | Detecting broadside acoustic signals with a fiber optical distributed acoustic sensing (DAS) assembly | |
| US9880047B2 (en) | Fiber optic distributed vibration sensing with directional sensitivity | |
| US9322702B2 (en) | Detecting the direction of acoustic signals with a fiber optical distributed acoustic sensing (DAS) assembly | |
| US9080949B2 (en) | Detecting broadside and directional acoustic signals with a fiber optical distributed acoustic sensing (DAS) assembly | |
| EP3314308B1 (en) | Method of calibrating depths of a seismic receiver array | |
| US20180031413A1 (en) | Fiber optic distributed acoustic sensor omnidirectional antenna for use in downhole and marine applications | |
| CN105277971A (en) | Micro-seismic monitoring system and method | |
| US10281606B2 (en) | Creating 3C distributed acoustic sensing data | |
| AU2013296677B2 (en) | Cable comprising twisted sinusoid for use in distributed sensing | |
| Dean et al. | Fibre optic based vibration sensing: Nature of the measurement | |
| Luo et al. | Microseismic monitoring using distributed optical fiber sensing techniques–An opportunity for coal burst risk management |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request |
Effective date: 20180720 |